Increased volume of dental pulp of permanent molar characterized by a crown body-root ratio equal or larger than 1:1 or an elongated pulp chambers and apical displacement of the bifurcation or trifurcation of the roots.

Hypohidrotic ectodermal dysplasia (HED) is characterized by hypotrichosis (sparseness of scalp and body hair), hypohidrosis (reduced ability to sweat), and hypodontia (congenital absence of teeth). The cardinal features of classic HED become obvious during childhood. The scalp hair is thin, lightly pigmented, and slow growing. Sweating, although present, is greatly deficient, leading to episodes of hyperthermia until the affected individual or family acquires experience with environmental modifications to control temperature. Only a few abnormally formed teeth erupt, at a later-than-average age. Physical growth and psychomotor development are otherwise within normal limits. Mild HED is characterized by mild manifestations of any or all the characteristic features.

Trichodentoosseous syndrome (TDO) is an autosomal dominant disorder with complete penetrance characterized by abnormalities involving hair, teeth, and bone (summary by Nguyen et al., 2013).

Increased volume of dental pulp of permanent molar characterized by a crown body-root ratio equal or larger than 1:1 or an elongated pulp chambers and apical displacement of the bifurcation or trifurcation of the roots.

In dentin dysplasia type I, both primary and secondary dentitions are affected. The color and general morphology of the teeth are usually normal, although they may be slightly opalescent and blue or brown. Teeth may be very mobile and exfoliate spontaneously because of inadequate root formation. On radiographs, the roots are short and may be more pointed than normal. Pulp chambers are usually absent except for a chevron-shaped remnant in the crown (Witkop, 1975). Root canals are usually absent. Periapical radiolucencies may be present at the apices of affected teeth, for reasons unknown. On light microscopic examination of the permanent teeth, the coronal dentin is normal, but further apically becomes irregular, fills the pulp chamber, and has a 'sand-dune' morphology. Scanning electron microscopic studies of the deciduous and permanent teeth have been reported (Sauk et al., 1972; Melnick et al., 1980). Subclassification of Dentin Dysplasia Type I O Carroll et al. (1991) and O Carroll and Duncan (1994) reviewed dentin dysplasia and proposed 4 subtypes of dentin dysplasia type I, which they designated as DD1a-d. In DD1a, there is complete obliteration of pulp chambers and no root development, with many periapical radiolucent areas. In DD1b, there are horizontal crescent-shaped radiolucent pulpal remnants and a few millimeters of root development, with many periapical radiolucent areas. DD1c shows 2 horizontal crescent-shaped radiolucent lines and significant but incomplete root development, with or without periapical radiolucent areas. DD1d is characterized by visible pulp chambers and oval pulp stones in the coronal third of the root canal with bulging of the root around the stones and few if any periapical radiolucent areas. The authors noted that the distinctions between the subtypes of DD1 were primarily useful clinically in terms of treatment options.

Oculodentodigital syndrome is characterized by a typical facial appearance and variable involvement of the eyes, dentition, and fingers. Characteristic facial features include a narrow, pinched nose with hypoplastic alae nasi, prominent columella and thin anteverted nares together with a narrow nasal bridge, and prominent epicanthic folds giving the impression of hypertelorism. The teeth are usually small and carious. Typical eye findings include microphthalmia and microcornea. The characteristic digital malformation is complete syndactyly of the fourth and fifth fingers (syndactyly type III) but the third finger may be involved and associated camptodactyly is a common finding (summary by Judisch et al., 1979). Neurologic abnormalities are sometimes associated (Gutmann et al., 1991), and lymphedema has been reported in some patients with ODDD (Brice et al., 2013). See review by De Bock et al. (2013). Genetic Heterogeneity of Oculodentodigital Syndrome An autosomal recessive form of ODDD (257850) is also caused by mutation in the GJA1 gene, but the majority of cases are autosomal dominant.

The TP63-related disorders comprise six overlapping phenotypes: Ankyloblepharon-ectodermal defects-cleft lip/palate (AEC) syndrome (which includes Rapp-Hodgkin syndrome). Acro-dermo-ungual-lacrimal-tooth (ADULT) syndrome. Ectrodactyly, ectodermal dysplasia, cleft lip/palate syndrome 3 (EEC3). Limb-mammary syndrome. Split-hand/foot malformation type 4 (SHFM4). Isolated cleft lip/cleft palate (orofacial cleft 8). Individuals typically have varying combinations of ectodermal dysplasia (hypohidrosis, nail dysplasia, sparse hair, tooth abnormalities), cleft lip/palate, split-hand/foot malformation/syndactyly, lacrimal duct obstruction, hypopigmentation, hypoplastic breasts and/or nipples, and hypospadias. Findings associated with a single phenotype include ankyloblepharon filiforme adnatum (tissue strands that completely or partially fuse the upper and lower eyelids), skin erosions especially on the scalp associated with areas of scarring, and alopecia, trismus, and excessive freckling.

Otodental syndrome is an autosomal dominant condition characterized by grossly enlarged canine and molar teeth (globodontia), associated with sensorineural hearing loss. Ocular coloboma segregating with otodental syndrome has been reported (summary by Gregory-Evans et al., 2007).

A very rare genetic overgrowth/obesity syndrome with characteristics of macrocephaly, obesity, mental (intellectual) disability and ocular abnormalities. Other frequent clinical signs include macrosomia, downslanting palpebral fissures, hypertelorism, broad nasal root, high and broad forehead and delay in bone maturation, in association with normal thyroid function and karyotype.

Ackerman syndrome has characteristics of pyramidal molar roots and taurodontism associated with variable anomalies. It has been described in two generations of one family. Both parents and their six siblings had pyramidal, taurodont or fused molar roots. Some of the patients also had hypotrichosis, an abnormal upper lip, thickened and wide philtrum, and/or juvenile glaucoma. Other features included entropion of the eyelid, syndactyly and clinodactyly of the fifth fingers.

Any amelogenesis imperfecta in which the cause of the disease is a mutation in the DLX3 gene.

Amelogenesis imperfecta is a disorder of tooth development. This condition causes teeth to be unusually small, discolored, pitted or grooved, and prone to rapid wear and breakage. Other dental abnormalities are also possible. These defects, which vary among affected individuals, can affect both primary (baby) teeth and permanent (adult) teeth.\n\nResearchers have described at least 14 forms of amelogenesis imperfecta. These types are distinguished by their specific dental abnormalities and by their pattern of inheritance. Additionally, amelogenesis imperfecta can occur alone without any other signs and symptoms or it can occur as part of a syndrome that affects multiple parts of the body.

Cranioectodermal dysplasia (CED) is a ciliopathy with skeletal involvement (narrow thorax, shortened proximal limbs, syndactyly, polydactyly, brachydactyly), ectodermal features (widely spaced hypoplastic teeth, hypodontia, sparse hair, skin laxity, abnormal nails), joint laxity, growth deficiency, and characteristic facial features (frontal bossing, low-set simple ears, high forehead, telecanthus, epicanthal folds, full cheeks, everted lower lip). Most affected children develop nephronophthisis that often leads to end-stage kidney disease in infancy or childhood, a major cause of morbidity and mortality. Hepatic fibrosis and retinal dystrophy are also observed. Dolichocephaly, often secondary to sagittal craniosynostosis, is a primary manifestation that distinguishes CED from most other ciliopathies. Brain malformations and developmental delay may also occur.

Hypoplastic amelogenesis imperfecta IA is characterized by enamel that may not develop to normal thickness. The enamel may have pits on the labial or buccal surfaces that are often arranged in rows and columns (see Witkop, 1989).

Cerebellofaciodental syndrome is an autosomal recessive neurodevelopmental disorder characterized by delayed development, intellectual disability, abnormal facial and dental findings, and cerebellar hypoplasia (summary by Borck et al., 2015).

Any tooth agenesis in which the cause of the disease is a mutation in the LRP6 gene.

Selective tooth agenesis-9 (STHAG9) is an autosomal dominant disorder characterized by agenesis of various teeth. Other features include taurodontism, microdontia, short tooth roots, sparse and slow-growing hair, and dry and itchy skin (Kantaputra et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of selective tooth agenesis, see STHAG1 (106600).

Hyperphosphatemic familial tumoral calcinosis (HFTC) is characterized by: Ectopic calcifications (tumoral calcinosis) typically found in periarticular soft tissues exposed to repetitive trauma or prolonged pressure (e.g., hips, elbows, and shoulders); and Painful swellings (referred to as hyperostosis) in the areas overlying the diaphyses of the tibiae (and less often the ulna, metacarpal bones, and radius). The dental phenotype unique to HFTC includes enamel hypoplasia, short and bulbous roots, obliteration of pulp chambers and canals, and pulp stones. Less common are large and small vessel calcifications that are often asymptomatic incidental findings on radiologic studies but can also cause peripheral vascular insufficiency (e.g., pain, cold extremities, and decreased peripheral pulses). Less frequently reported findings include testicular microlithiasis and angioid streaks of the retina.

Snijders Blok-Campeau syndrome (SNIBCPS) is an autosomal dominant neurodevelopmental disorder characterized by global developmental delay with impaired intellectual development and delayed speech acquisition. Affected individuals tend to have expressive language deficits, with speech apraxia and dysarthria. Other features include macrocephaly and characteristic facial features, such as prominent forehead and hypertelorism, hypotonia, and joint laxity. The severity of the neurologic deficits and presence of nonneurologic features is variable (summary by Snijders Blok et al., 2018).